A multiple gestation is a pregnancy in which a woman carries more than one fetus. Multiple gestations are concerning because women who are expecting more than one baby are at increased risk of certain pregnancy complications, including preterm delivery. Some of the complications associated with multiple gestation can be minimized if they are detected and diagnosed early.
The embryonic heart starts beating twenty-two days after conception. The heart at this stage may be too small to hear. By the ninth or tenth week after the last menstrual period of the expecting mother, one is more likely to be able to hear the heartbeat of the fetus. By the twelve week, the heartbeat can usually be heard consistently by using a Doppler instrument for amplification.
Although the human ear is unequalled in detecting sounds over a particular frequency range, the spectrum occupied by fetal heart sounds is on the threshold of audibility. This aural processing has always caused problems relating to degree and accuracy of fetal auscultation. Electronically processing the fetal phonocardiogram (“FPCG”) presents a way of avoiding these problems. The greater low frequency sensitivity of the phonocardiographic transducer captures all the acoustic information generated by the fetal heart. Then, additional visual examination of the FPCG provides an effective way of determining temporal measures of fetal cardiac function.
The FPCG allows the measurement of the instantaneous fetal heart rate, beat-to-beat differences and duration of systolic and diastolic phases. These measures are sensitive indicators of cardiac function, reflecting fetal well-being. With the record of various critical cardiac activities readily available, some abnormalities of the fetal heart can be detected in the early stages of the pregnancy. A problem arises with the detection of the abnormalities of the fetal heart in the event of a multiple gestation. When more than one fetus is present in a mother's womb, the acoustic transducer (acoustic or electronic stethoscope) captures multiple FPCGs. As one shortcoming, it is difficult to clearly discern the heart sounds from one fetus in the mother's womb from the heart sounds of another fetus in the mother's womb.
Thus, a need exists for a capability to discern a heart sound of one fetus from the heart sound of another fetus.